What's Up with the Granary?

What was the so-called granary used for? There are twelve rooms in this 50 by 40 meter building. It was built on a giant mud-brick platform between 2200 and 2300 BCE, but there is an earlier building under at least one section. Between the rooms are sleeper walls. Excavations in 1998-2000 of this area led to no discovery of grain or pots. At Harappa this structure is next to the equally mysterious "workingmen's platforms" where we think some sort of labor involving water took place (but no traces of indigo dye are found). At Mohenjo-daro, this structure is next to the Great Bath. What purpose do you think it could have served?